Was LUCA (Last Universal Common Ancestor) of all living things was an asexually single celled organism?

If so, are their reliable evidence--not opinions-- how its decendants transitioned to sexually reproducing organisms?


delete "was an". replace with "an"

7 Answers

  • CRR
    Lv 7
    4 weeks ago
    Favorite Answer

    LUCA is a hypothetical organism that "had to" exist if the theory of evolution is true. But how it transitioned to sexually reproducing organisms is an evolutionary fairy tail.

  • cosmo
    Lv 7
    4 weeks ago

    Yes, LUCA might have been a lithophagic extremophile that managed to survive the major asteroid strikes of the pre-Cambrian.  (The oceans boiled away, dry to the bottom, about three time as a result of the energy deposited by asteroid strikes.)

    Many bacteria exchange genetic material by the process of "conjugation", where two bacteria of the same "species" link together and share genetic material.  It's sort of like sex, except that the bacteria are similar.  It's a small change from that to a system where the two organisms have different "sex" characteristics, i.e. different expression of the same genetic material in a way that enhances the fitness of the species.  The next step for mulit-cellular colonies is to produce a great number of low-cost single-celled gametes that each carry and represent the entire genetic makeup of the colony.

    The "Cambrian explosion" resulted from the origins of sex.  Originally, there were few genetic safeguards against inter-species hybridization, and so pretty much everything was exchanging genetic material with everything else, not necessarily within the confines of a single species --- usually leading to a bad result, but greatly increasing the rate of genetic change and the processes of evolution.  Sexual reproduction speeds up evolution tremendously, and is therefore an excellent enhancement for survival.

  • 4 weeks ago

    Yes, for the most part. Sexual reproduction evolved as a way to mix genetic material between members of the same species, as to provide their offspring an advantage over the competition. By doing so, a lot more genetic diversity was allowed to take hold, and thus evolution was able to do its thing in allowing said organisms to survive and spread. It was such an evolutionary advantage that most life we see today on the macro scale was descendant of such a hypothetical organism.

  • 4 weeks ago

    > Was LUCA (Last Universal Common Ancestor) of all living things an asexual single celled organism?

    Most likely yes.  LUCA would have been before Bacteria and Archaea diverged.  Most of those guys are free-living single-celled today.  It's pretty safe to bet that the LUCA would have been single-celled too.

    > If so, are their reliable evidence--not opinions-- how its descendents transitioned to sexually reproducing organisms?

    LOL.  Once you accept that that there was a LUCA, and you find that some life today reproduces sexually, then you realize that there must have been living organisms between those things.

    Some developments between those things would involve:

    o keeping DNA in more than one chromosome, within a cell.

    o development of mitosis.

    o diploidy

    o development of meiosis

    o fusion of mating strain cells which would return a haploid generation to diploidy.

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  • MARK
    Lv 7
    4 weeks ago

    A clear question would help. Ask waht you mean and do not try to wrap it up in clever sounding terminology.

    Do you want to know how sexually reproducing organisms evolved? Is that your actual question?

    If it is I recommend you post that question on the forum. I am not attempting to answer a question at which I have to second guess what you are asking.

  • 4 weeks ago

    That is a presumption, that all life came from some original life.  It is easier to accept than the idea that life developed multiple times but was effectively the same thing after each individual developmental event, so all life is actually descended from many different unique original sources that were indistinguishable at each specific time of origin.

    As to the evidence for how life evolved and developed over time, that is obtained by examination of the fossil record and the idea of ontogeny recapitulates phylogeny (the developing (embryonic) life form passes through its various past forms as it matures into whatever type of life it is today).  There is, of course, extensive evidence from genetic studies that allow linking of life forms in some grand scheme.  We also can look at existing life forms and use them as analogies for past life forms, and derive a chain of descent concept.

    They are all interpretations though.  There is no "definitive" answer but we can find some pretty likely explanations.  The only real way to prove, beyond any doubt, how life evolved is to live through the process and observe it first-hand, and well, that is impossible.  So, we use logic and interpret.  Cannot do better.  We can never KNOW beyond any doubt.  We can definitely exclude lots of possibilities though.

  • Zirp
    Lv 7
    4 weeks ago

    There are bacteria that sometimes exchange genetic material before splitting themselves up

    There are hermafrodite snails that have the strongest partner dump "sperm" into the weaker one

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